A multilayer ceramic capacitor normally comprises a laminated body including ceramic layers made of a dielectric material and external electrodes, some of the ceramic layers having internal electrodes thereon. The ceramic layers are stacked together in a manner that the internal electrodes are alternately exposed at opposite sides of the laminated body. The external electrodes are disposed at the end portions including the opposite sides of the laminated body and are connected to respective sets of internal electrodes of the laminated body.
FIG. 3 illustrates a typical arrangement of a laminated body 3 of such a multilayer ceramic capacitor. The laminated body 3 is formed by stacking ceramic layers 7 having internal electrodes 5 and 6 and made of a dielectric material, and a plurality of bare ceramic layers 7′ without any internal electrodes. The bare ceramic layers 7′ without any internal electrodes may be called dummy sheets. The ceramic layers 7 are stacked in a manner to have the internal electrodes 5 and 6 alternately exposed at opposite sides of the laminated body 3. A number of dummy sheets are disposed on top of the uppermost ceramic layer 7 as well as below the undermost ceramic layer 7. As shown in FIG. 1, a pair of external electrodes 2 are, respectively, disposed at the opposite end portions of the laminated body 3 and are connected to the internal electrodes 5 and 6.
The process for manufacturing such a multilayer ceramic capacitor in accordance with the prior art will now be described.
First, an amount of slurry is prepared by mixing fine ceramic powder with an organic binder. Then, a ceramic green sheet is obtained by thinly casting the slurry on a carrier film comprised of, e.g., polyethylene terephthalate film by using a doctor blade method. Next, the ceramic green sheet on the carrier film is dried and cut by using a cutting head into a plurality of ceramic green sheets of a desired size. Then a conductive paste for internal electrodes is printed on the surfaces of the ceramic green sheets and dried. As a result, as shown in FIG. 6, a plurality of ceramic green sheets 1a, 1b having internal electrode patterns 2a and 2b printed thereon lengthwise and widthwise are obtained.
Subsequently, the ceramic green sheets 1a, 1b having the internal electrode patterns 2a and 2b are stacked and a number of bare ceramic green sheets 1 without any internal electrode patterns are stacked both on top of the uppermost ceramic green sheet 1a and below the undermost ceramic green sheet 1b. Then, a laminated ceramic body is obtained by pressing the stacked ceramic green sheets. The ceramic green sheets 1a and 1b are stacked in a manner that the internal electrode patterns 2a of the ceramic green sheets 1a are shifted with respect to the internal electrode patterns 2b of the ceramic green sheets 1b by half a pattern size along lengthwise. Thereafter, the laminated ceramic body is diced into a number of unsintered laminated bodies, each having a desired size. The unsintered laminated bodies are then sintered to obtain the laminated bodies 3.
Next, a conductive paste is applied on opposite end portions of the laminated body 3 and baked to form conductive films. A pair of external electrodes 2 is formed on opposite end portions, as shown in FIG. 1, by plating the surface of the conductive film.
FIG. 2 shows a partial cross-sectional view of the laminated body of a multilayer ceramic capacitor. In the laminated body of the prior art multilayer ceramic capacitor, empty spaces between conductive particles shown in FIG. 2 are generally filled with ceramic particles.
However, the expansion or shrinkage rate of the ceramic layers 7 caused by temperature changes may be different from that of the internal electrodes 5 and 6, which may in turn cause micro cracks developed in the laminated body 3. Such tendency may become rather serious when the laminated body 3 includes, e.g., more than a hundred layers. Especially, when the multilayer ceramic capacitors are soldered on a circuit board for the manufacture of end products such as cellular phone, cracks can be developed in the laminated body 3.